"Our challenge is to make sure every child in America is learning from an effective teacher, no matter what it takes," Duncan told officials and local delegates of the National Education Association at their annual meeting in San Diego. "So today, I ask you to join President Obama and me in a new commitment to results that recognizes and rewards success in the classroom and is rooted in our common obligation to children."

The issues of performance-based pay and the tests used to evaluate teachers continue to concern union members, as was evident by the questions asked of the secretary during a town hall-style question-and-answer session. While Duncan noted that teacher evaluations should never be based entirely on test scores, he was firm in saying that students' performance must play a role.

"I understand that tests are far from perfect and that it is unfair to reduce the complex, nuanced work of teaching to a simple multiple choice exam," Duncan told the crowd of 6,500. "Test scores alone should never drive evaluation, compensation or tenure decisions. That would never make sense. But to remove student achievement entirely from evaluation is illogical and indefensible."

"School systems pay teachers billions of dollars more each year for earning credentials that do very little to improve the quality of teaching," Duncan said. "At the same time, many schools give nothing at all to the teachers who go the extra mile and make all the difference in students' lives. Excellence matters, and we should honor it -- fairly, transparently and on terms teachers can embrace."

Asked where the union might compromise on the issue of merit-based pay, NEA president Dennis Van Roekel deflected to the local level.

"I have no problem with [Duncan] raising that issue, but where it's going to be decided is in local school districts," he told ABC News. "And where we support it is, if our local association bargains an alternative compensation system, we're going to support them. But the idea that somebody on the outside is going to say, 'Here's what you all ought to do,' I mean that's not going to work.

"What's important to us, and what we like, is that the issue of compensation has been heightened," Van Roekel added. "We need to change the compensation of educators in America. We're not going to be successful at recruiting the number and quality we need in the years ahead, so the idea that we have more focus on compensation and the need for higher salaries, we need that."

Others were not as kind.

"Quite frankly, merit pay is union-busting," said one delegate in the audience, to applause.

"I believe that teacher unions are at a crossroads," he said. "These policies were created over the past century to protect the rights of teachers, but they have produced an industrial, factory model of education that treats all teachers like interchangeable widgets.

"When inflexible seniority and rigid tenure rules that we designed put adults ahead of children, then we are not only putting kids at risk, we're putting the entire education system at risk," he added. "We're inviting the attack of parents and the public, and that is not good for any of us."

While the Obama administration has emphasized performance-based pay in the past, Duncan seemingly acknowledged he is entering sensitive territory for the teachers' unions, joking halfway through his remarks that, "You can boo, but just don't throw any shoes, please."

Duncan's speech was the fourth and final to outline the reform strategies that states must address under the American recovery and Reinvestment Act and the criteria to compete for a portion of the $4.35 billion "Race to the Top" funds to improve education quality.

The secretary's previous speeches addressed the use of data to inform instruction and education policy decisions, the need for standards and assessments, and the role of charter schools in turning around low-performing schools.